The Kashyyyk Royal Families were princely Wookiee kindreds on their homeworld of Kashyyyk.
Among the responsibilities of the Royal Families was deciding on the planet's stance in time of war. In 21 BBY, at the outbreak of the Clone Wars, their representatives accordingly met in the Kashyyyk Royal City, in a council dominated by King Grakchawwaa.
It is unclear on current evidence what the exact constitutional structure of Kashyyyk at this time was: the council seemed to defer to Grakchawwaa's opinion, but there were evidently several Royal Families functioning as a collective decision-making group, and it is unclear what the exact reasons for Grakchawwaa's seniority were.
Initially, Grakchawwaa decided to maintain neutrality, but when news arrived that Separatist battle droids had killed his son, he angrily committed himself to war on the side of the Republic, and led his planet into the conflict.